#!/usr/bin/python
#
# Copyright (C) 2008 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


"""MockService provides CRUD ops. for mocking calls to AtomPub services.

  MockService: Exposes the publicly used methods of AtomService to provide
      a mock interface which can be used in unit tests.
"""

import atom.service
import pickle


__author__ = 'api.jscudder (Jeffrey Scudder)'


# Recordings contains pairings of HTTP MockRequest objects with MockHttpResponse objects.
recordings = []
# If set, the mock service HttpRequest are actually made through this object.
real_request_handler = None

def ConcealValueWithSha(source):
    import sha
    return sha.new(source[:-5]).hexdigest()

def DumpRecordings(conceal_func=ConcealValueWithSha):
    if conceal_func:
        for recording_pair in recordings:
            recording_pair[0].ConcealSecrets(conceal_func)
    return pickle.dumps(recordings)

def LoadRecordings(recordings_file_or_string):
    if isinstance(recordings_file_or_string, str):
        atom.mock_service.recordings =  pickle.loads(recordings_file_or_string)
    elif hasattr(recordings_file_or_string, 'read'):
        atom.mock_service.recordings = pickle.loads(
          recordings_file_or_string.read())

def HttpRequest(service, operation, data, uri, extra_headers=None,
    url_params=None, escape_params=True, content_type='application/atom+xml'):
    """Simulates an HTTP call to the server, makes an actual HTTP request if
    real_request_handler is set.

    This function operates in two different modes depending on if
    real_request_handler is set or not. If real_request_handler is not set,
    HttpRequest will look in this module's recordings list to find a response
    which matches the parameters in the function call. If real_request_handler
    is set, this function will call real_request_handler.HttpRequest, add the
    response to the recordings list, and respond with the actual response.

    Args:
      service: atom.AtomService object which contains some of the parameters
          needed to make the request. The following members are used to
          construct the HTTP call: server (str), additional_headers (dict),
          port (int), and ssl (bool).
      operation: str The HTTP operation to be performed. This is usually one of
          'GET', 'POST', 'PUT', or 'DELETE'
      data: ElementTree, filestream, list of parts, or other object which can be
          converted to a string.
          Should be set to None when performing a GET or PUT.
          If data is a file-like object which can be read, this method will read
          a chunk of 100K bytes at a time and send them.
          If the data is a list of parts to be sent, each part will be evaluated
          and sent.
      uri: The beginning of the URL to which the request should be sent.
          Examples: '/', '/base/feeds/snippets',
          '/m8/feeds/contacts/default/base'
      extra_headers: dict of strings. HTTP headers which should be sent
          in the request. These headers are in addition to those stored in
          service.additional_headers.
      url_params: dict of strings. Key value pairs to be added to the URL as
          URL parameters. For example {'foo':'bar', 'test':'param'} will
          become ?foo=bar&test=param.
      escape_params: bool default True. If true, the keys and values in
          url_params will be URL escaped when the form is constructed
          (Special characters converted to %XX form.)
      content_type: str The MIME type for the data being sent. Defaults to
          'application/atom+xml', this is only used if data is set.
    """
    full_uri = atom.service.BuildUri(uri, url_params, escape_params)
    (server, port, ssl, uri) = atom.service.ProcessUrl(service, uri)
    current_request = MockRequest(operation, full_uri, host=server, ssl=ssl,
        data=data, extra_headers=extra_headers, url_params=url_params,
        escape_params=escape_params, content_type=content_type)
    # If the request handler is set, we should actually make the request using
    # the request handler and record the response to replay later.
    if real_request_handler:
        response = real_request_handler.HttpRequest(service, operation, data, uri,
            extra_headers=extra_headers, url_params=url_params,
            escape_params=escape_params, content_type=content_type)
        # TODO: need to copy the HTTP headers from the real response into the
        # recorded_response.
        recorded_response = MockHttpResponse(body=response.read(),
            status=response.status, reason=response.reason)
        # Insert a tuple which maps the request to the response object returned
        # when making an HTTP call using the real_request_handler.
        recordings.append((current_request, recorded_response))
        return recorded_response
    else:
        # Look through available recordings to see if one matches the current
        # request.
        for request_response_pair in recordings:
            if request_response_pair[0].IsMatch(current_request):
                return request_response_pair[1]
    return None


class MockRequest(object):
    """Represents a request made to an AtomPub server.

    These objects are used to determine if a client request matches a recorded
    HTTP request to determine what the mock server's response will be.
    """

    def __init__(self, operation, uri, host=None, ssl=False, port=None,
        data=None, extra_headers=None, url_params=None, escape_params=True,
        content_type='application/atom+xml'):
        """Constructor for a MockRequest

        Args:
          operation: str One of 'GET', 'POST', 'PUT', or 'DELETE' this is the
              HTTP operation requested on the resource.
          uri: str The URL describing the resource to be modified or feed to be
              retrieved. This should include the protocol (http/https) and the host
              (aka domain). For example, these are some valud full_uris:
              'http://example.com', 'https://www.google.com/accounts/ClientLogin'
          host: str (optional) The server name which will be placed at the
              beginning of the URL if the uri parameter does not begin with 'http'.
              Examples include 'example.com', 'www.google.com', 'www.blogger.com'.
          ssl: boolean (optional) If true, the request URL will begin with https
              instead of http.
          data: ElementTree, filestream, list of parts, or other object which can be
              converted to a string. (optional)
              Should be set to None when performing a GET or PUT.
              If data is a file-like object which can be read, the constructor
              will read the entire file into memory. If the data is a list of
              parts to be sent, each part will be evaluated and stored.
          extra_headers: dict (optional) HTTP headers included in the request.
          url_params: dict (optional) Key value pairs which should be added to
              the URL as URL parameters in the request. For example uri='/',
              url_parameters={'foo':'1','bar':'2'} could become '/?foo=1&bar=2'.
          escape_params: boolean (optional) Perform URL escaping on the keys and
              values specified in url_params. Defaults to True.
          content_type: str (optional) Provides the MIME type of the data being
              sent.
        """
        self.operation = operation
        self.uri = _ConstructFullUrlBase(uri, host=host, ssl=ssl)
        self.data = data
        self.extra_headers = extra_headers
        self.url_params = url_params or {}
        self.escape_params = escape_params
        self.content_type = content_type

    def ConcealSecrets(self, conceal_func):
        """Conceal secret data in this request."""
        if self.extra_headers.has_key('Authorization'):
            self.extra_headers['Authorization'] = conceal_func(
              self.extra_headers['Authorization'])

    def IsMatch(self, other_request):
        """Check to see if the other_request is equivalent to this request.

        Used to determine if a recording matches an incoming request so that a
        recorded response should be sent to the client.

        The matching is not exact, only the operation and URL are examined
        currently.

        Args:
          other_request: MockRequest The request which we want to check this
              (self) MockRequest against to see if they are equivalent.
        """
        # More accurate matching logic will likely be required.
        return (self.operation == other_request.operation and self.uri ==
            other_request.uri)


def _ConstructFullUrlBase(uri, host=None, ssl=False):
    """Puts URL components into the form http(s)://full.host.strinf/uri/path

    Used to construct a roughly canonical URL so that URLs which begin with
    'http://example.com/' can be compared to a uri of '/' when the host is
    set to 'example.com'

    If the uri contains 'http://host' already, the host and ssl parameters
    are ignored.

    Args:
      uri: str The path component of the URL, examples include '/'
      host: str (optional) The host name which should prepend the URL. Example:
          'example.com'
      ssl: boolean (optional) If true, the returned URL will begin with https
          instead of http.

    Returns:
      String which has the form http(s)://example.com/uri/string/contents
    """
    if uri.startswith('http'):
        return uri
    if ssl:
        return 'https://%s%s' % (host, uri)
    else:
        return 'http://%s%s' % (host, uri)


class MockHttpResponse(object):
    """Returned from MockService crud methods as the server's response."""

    def __init__(self, body=None, status=None, reason=None, headers=None):
        """Construct a mock HTTPResponse and set members.

        Args:
          body: str (optional) The HTTP body of the server's response.
          status: int (optional)
          reason: str (optional)
          headers: dict (optional)
        """
        self.body = body
        self.status = status
        self.reason = reason
        self.headers = headers or {}

    def read(self):
        return self.body

    def getheader(self, header_name):
        return self.headers[header_name]
